We intend to further examine the various factors that appear to be connected with adverse reactions to the contrast media and to explore the relation existing between molecular structure, toxicity and distribution to the various tissues. We also intend to further pursue the synthesis of new compounds based on information gleaned earlier regarding toxicity and tissue distribution. New compounds bearing a higher total number of iodine atoms than has been the case with current media will be explored. These will be screened in a preliminary way by enzyme inhibition studies and other new approaches developed in this laboratory.